PROJECT SUMMARY/ABSTRACT: This integrated research and training plan will prepare Dr. Chai, a practicing emergency medicine physician to become an independent, NIH funded physician-researcher with expertise in smartphone medication adherence intervention-based HIV prevention strategies directed toward individuals with substance use disorders. Despite advances in HIV prevention, testing and behavioral health, the epidemic of HIV continues to affect men who have sex with men (MSM) in greater proportion compared to heterosexual individuals. Among MSM, those with concomitant stimulant use (MSM+S) experience greater risk of condomless sex, disengagement with care, additional substance use and medication nonadherence. Interventions targeting these risk factors among MSM+S have modest effects that diminish over time. In 2010, the iPrEX study demonstrated a 40% reduction in HIV transmission in MSM individuals who adhered to pre-exposure prophylaxis (PrEP) with tenofovir/emtricitabine (TDF/FTC). Data from the iPrEX study demonstrates that with consistent adherence, MSM can achieve a greater than 90% protection from HIV. PrEP, therefore is an attractive option and accepted among MSM, but adherence remains difficult, especially among MSM with stimulant use. HIV prevention strategies integrating real-time PrEP adherence data and behavioral interventions to address stimulant use and medication adherence among MSM+S may improve adherence and prevent subsequent HIV infection. Under guidance of a strong team of NIH-funded researchers, Dr. Chai will achieve three training goals that integrate into the specific aims of his research plan. (1) Gain experience in crafting behavioral interventions with a particular focus on HIV and PrEP, (2) Gain experience designing, conducting and evaluating clinical trials in MSM on PrEP, and (3) Learn qualitative research methods and analysis techniques. Dr. Chai?s training activities will be complemented by an innovative research plan that will help him gain practical experience of his new skills. In a tiered approach, Dr. Chai will first inform the specification of a smartphone-based adherence intervention (PrEPsteps) with participant-generated content solicited through focus groups. Next, he will test the feasibility, acceptability and potential for an effect of PrEPsteps on PrEP adherence compared to treatment as usual in a pilot randomized controlled trial (N=60) of MSM+S on PrEP. Finally, Dr. Chai will assess the acceptability of the PrEPsteps intervention components (and the digital pill) through qualitative exit interviews with those randomized to the PrEPsteps condition. This innovative K23 Mentored Patient Oriented Career Development Award responds to NIH high priority topics in HIV/AIDS (NOT- OD-15-137) by developing a novel adherence intervention that innovatively responds to vivid, real-time feedback of PrEP adherence from a digital pill, thereby reducing the incidence of HIV/AIDS among MSM+S.